In producing petroleum and other useful fluids from production wells, a variety of component combinations, sometimes referred to as completions, are used in the downhole environment. For example, it is generally known to deploy a submergible pumping system in a well to raise the production fluids to the earth's surface.
In this latter example, production fluids enter the wellbore via perforations formed in a well casing adjacent a production formation. Fluids contained in the formation collect in the wellbore and are raised by the submergible pumping system to a collection point above the surface of the earth. In an exemplary submergible pumping system, the system includes several components such as a submergible electric motor that supplies energy to a submergible pump. This system may further include additional components, such as a motor protector, for isolating the motor oil from well fluids. A connector also is used to connect the submergible pumping system to a deployment system. These and other components may be combined in the overall submergible pumping system.
Conventional submergible pumping systems are deployed within a wellbore by a deployment system that may include tubing, cable or coil tubing. Power is supplied to the submergible electric motor via a power cable that runs along the deployment system. For example, with coil tubing, the power cable is either banded to the outside of the coil tubing or disposed internally within the hollow interior formed by the coil tubing. Additionally, other control lines, such as hydraulic control lines and tubing encapsulated conductors (TECs) may extend along or through the deployment system to provide a variety of inputs or communications with various components of the completion.
When an electric submergible pumping system is deployed in a well, it often is convenient to utilize coil tubing to support the completion equipment and to channel power and other conductors, particularly when production fluids are located a substantial distance beneath the earth's surface. However, the weight of the coil tubing, power cable, any fluid within the coil tubing, control lines and completion equipment determines the length of coil tubing that can support the completion in the well, eventually reaching the material strength limit of the tubing. Accordingly, it is desirable to minimize forces associated with deploying and retrieving a completion, so that the coil tubing may be deployed to maximum depth without risking damage to the coil tubing or power cable.
For removal of the completion from the well, such factors must be considered as adding to the load which will be exerted on the deployment system. Other loads are also encountered upon retrieval. For example, a coil tubing deployment system may be filled with an internal fluid to provide buoyancy to the power cable running therethrough. However, the "loaded" coil tubing cannot be extended as far into a well as an unloaded coil tubing deployment system, because the weight of the internal fluid places additional force on the coil tubing. The fluid also adds to the load borne by the deployment system upon retrieval. Other forces and loads may result from drag within the wellbore (such as due to integral packers and similar structures), accumulated sand or silt, rock or aggregate fall-ins, and so forth. To provide for such loads, the deployment system is generally overdesigned or the completion is positioned substantially higher in the well than the mechanical strength limits of the deployment system would otherwise dictate.
When a submergible pumping system is deployed to substantial depth relative to the strength of the coil tubing, it has been proposed to release the completion and remove the coil tubing from the well separately from the completion. A work string, such as a high tensile strength coil tubing with a fishing tool, is then run downhole and latched to the completion for removal. Conventionally, submergible pumping systems have been separated from the coil tubing at the connector used to connect the coil tubing to the completion. Conventional connectors had separable components connected by shear pins or other frangible structures. Thus, to release the deployment system from the submergible pumping system, sufficient force was exerted on the deployment system to shear the pins. However, the strength to withstand the additional load required to produce this shear force must also be built into the deployment system. Moreover, this additional load potentially can damage the coil tubing and power cable. To avoid such damage, the length of the coil tubing must again be reduced to correspondingly reduce the weight supported in the wellbore. Such limits on the depth to which the submergible pumping system can be deployed are undesirable.
It would be advantageous to have a remotely actuated separation technique for releasing a deployment system from a completion, e.g. submergible pumping system, without placing undue added forces on the deployment system during the separation operation. Such a technique for separating the deployment system from the completion would facilitate placement of the completion at greater depth within the wellbore without otherwise changing the deployment system or submergible components.